Dry eye is a condition that affects millions of people. More than 40 million people in North America have some form of dry eye, and many millions more suffer worldwide. Dry eye results from the disruption of the natural tear film on the surface of the eye, and can result in ocular discomfort, visual disturbance and a reduction in vision-related quality of life. Activities of daily living such as driving, computer use, housework, and reading have also been shown to be negatively impacted by dry eye. Patients with severe cases of dry eye are at risk for serious ocular health deficiencies such as corneal ulceration, and can experience a quality of life deficiency comparable to that of moderate-severe angina.
Dry Eye Disease (“DED”) is a clinical condition of the eye. DED is progressive in nature, and fundamentally results from insufficient tear coverage on the surface of the eye. This poor tear coverage prevents healthy gas exchange and nutrient transport for the ocular surface, promotes cellular desiccation, and creates a poor refractive surface for vision. Poor tear coverage typically results from: 1) insufficient aqueous tear production from the lacrimal glands (e.g. secondary to post-menopausal hormonal deficiency, autoimmune disease, LASIK surgery, etc.), and/or 2) excessive evaporation of aqueous tear resulting from dysfunction of the meibomian glands. Low tear volume causes a hyperosmolar environment that induces an inflamed state of the ocular surface. This inflammatory response induces apoptosis of the surface cells, which in turn prevents proper distribution of the tear film on the ocular surface so that any given tear volume is rendered less effective. This initiates a vicious cycle where more inflammation can ensue, causing more surface cell damage, etc.
External factors that are not clinically based may also contribute to dry eye. These factors can include medications, dehydration, and environmental pollutants. Contact lenses, particularly soft contact lenses, are also known to cause or exacerbate the symptoms of dry eye. The contact lenses continually absorb water from the surface of the tear film in order to keep hydrated, leading to dryness of the eye. Dry eye can also be a symptom of the condition commonly known as “tired eye.” During extended periods of focused, intense use, such as heavy computer use and long distance driving, the eyes strain and blink less frequently, which can lead to insufficient lubrication of the eyes (i.e., dry eye).
There is a wide spectrum of treatments for dry eye, although without substantial efficacy for treatment of the condition. Treatment options include: artificial tear substitutes, ointments, gels, warm compresses, environmental modification, topical cyclosporine, omega-3 fatty acid supplements, punctal plugs, and moisture chamber goggles. Patients with severe disease may further be treated with punctal cautery, systemic cholinergic agonists, systemic anti-inflammatory agents, mucolytic agents, autologous serum tears, PROSE scleral contact lenses, and tarsorrhaphy. Despite these treatment options, dry eye continues to be considered one of the most poorly treated diseases in ophthalmology. Accordingly, it would be desirable to have a more effective treatment for dry eye.